<!DOCTYPE html>
<html lang="zh-CN">

<head>
    <meta charset="utf-8">
    <meta http-equiv="X-UA-Compatible" content="IE=edge">
    <meta name="viewport" content="width=device-width, initial-scale=1, maximum-scale=1, user-scalable=no">
    <meta name="author" content="何毓堂">
    <title></title>
    <link rel="stylesheet" type="" href="">
    <style>
        div {
            width: 380px;
            height: 500px;
            margin: 0 auto;
            text-align: center;
        }

        ul {
            list-style: none;
            padding: 0;
            margin: 0;
        }

        li {
            width: 80px;
            height: 82px;
            border: 1px solid violet;
            border-radius: 10px;
        }

        nav {
            display: flex;
        }

        .show {
            width: 265px;
            height: 265px;
            border: 1px solid violet;
        }

        .endways {
            /* display: column; */
            margin-left: 15px;
        }

        .endways li {
            margin-top: 6px;
        }

        .below {
            width: 370px;
            display: flex;
            flex-wrap: wrap;
            margin-top: 5px;
        }

        .below li {
            margin-left: 8px;
            margin-top: 10px;
        }

        img {
            width: 80px;
            height: 82px;
            top: -30px;
            border-radius: 10px;
        }

        .largen {
            width: 265px;
            height: 265px;
        }
    </style>
</head>

<body>
    <div>
        <nav>
            <ul>
                <li class="show"><img src="img\big_1.jpg" alt="" class="largen"></li>
            </ul>
            <ul class="endways">
                <li><img src="img\big_1.jpg" alt=""></li>
                <li><img src="img\big_2.jpg" alt=""></li>
                <li><img src="img\big_3.jpg" alt=""></li>
            </ul>
        </nav>
        <ul class="below">
            <li><img src="img\big_4.jpg" alt=""></li>
            <li><img src="img\big_5.jpg" alt=""></li>
            <li><img src="img\big_6.jpg" alt=""></li>
            <li><img src="img\big_7.jpg" alt=""></li>
            <li><img src="img\big_8.jpg" alt=""></li>
            <li><img src="img\big_9.jpg" alt=""></li>
            <li><img src="img\big_10.jpg" alt=""></li>
            <li><img src="img\big_11.jpg" alt=""></li>
        </ul>
    </div>
</body>

</html>
<script>
    var imgs = document.querySelectorAll('img');
    for (var i = 0; i < imgs.length; i++) {
        imgs[i].index = i;

        imgs[i].onmouseover = function () {
            console.log(this.index);
            if (imgs[this.index] != 0) {
                imgs[0].src = imgs[this.index].src;
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</script>